1. Field of the Invention
This invention relates to a capacitance type displacement sensor which is used to detect a displacement of an object, such as tilt angle, acceleration, position etc., for example.
2. Related Background Art
Displacement gauges of the prior art include contact-type and non-contact type devices.
The contact-type displacement gauge has a construction that a brush 61 secured to the tip of a pendulum 60 is slid in contact with a resistor 62 which is supplied with a constant voltage as shown in FIG. 1, and voltages into which the constant voltage is divided by the brush 61 are output as a detection output to detect a tilt angle.
On the other hand, as shown in FIG. 2, the non-contact type displacement gauge has a construction that a magnet 71 secured to the tip of a pendulum 60 is swung along side magnetic resistant elements 72 and 73 without contacting with the magnetic resistant elements 72, 73, and a tilt angle is differentially detected on the basis of the variation in resistant values of the magnetic resistant elements 72 and 73.
The contact-type displacement gauge as described above is a displacement gauge in which a contact portion such as a brush is displaced along a resistor while contacting the resistor to thereby output a voltage obtained by split resistance, and it has a limited life time because it is operated in a contact mode. A rotational torque is increased due to friction of the contact portion, so that an output has large hysteresis. Conversely, in order to reduce the hysteresis, a larger deadweight or a longer arm is required, so that the displacement gauge becomes more enormous and weighty. Therefore, the contact-type displacement gauge has problems in its durability and detection accuracy for displacement amount.
In the non-contact type displacement gauge, the problem as described above does not occur. However, the magnetic characteristic of the magnet is liable to be deteriorated with time lapse, so that there are problems in detection accuracy and durability. In addition, the magnetic resistant element is formed of a semiconductor and thus its temperature characteristic is degraded, so that an appropriate temperature compensation must be considered for use over a broad temperature range.